1. Field of the Invention
The invention relates to an adjustment armature for seats with an adjustable inclinable backrest, in particular, for motor vehicles seats, wherein a fixed armature part correlated with the seat part and an adjustable armature part correlated with the backrest are connected to one another by an actuating member, wherein an adjusting and locking device, determining the position of both armature parts relative to one another and configured as a gear, is provided, and wherein the actuating member comprises an eccentric segment on which one of the armature parts is supported while the other-armature part supports the eccentric segment, which eccentric segment is comprised of two wedge segments covering partially a driver and inclined relative to one another, of a driver segment engaged between their narrow sides, and of a force storage means forcing the wide sides of the wedge segments apart, wherein the actuating member, if necessary, has a central receptacle for a fixed connection with a transmission rod.
2. Description of the Related Art
From DE 44 36 101 A1 an adjustment armature of the aforementioned kind is known in which the inner surfaces of the wedge segments are supported on a projecting collar correlated with the fixed armature part. The outer surfaces of the wedge segments are surrounded by a bearing bushing which is fixedly connected to the armature part of the backrest. For driving the eccentric segment a driver arm projecting from the driver engages between the narrow sides of the two wedge segments while the driver itself is supported in the projecting collar of the fixed armature part. In this connection, the wedge segments are forced apart by a spring element acting on the wide sides positioned opposite the driver arm in the direction of maintaining the eccentricity. In order to allow for a compensation movement of the eccentricity in the case of unavoidable manufacturing tolerances at the bearing locations and the toothing of the armature parts during adjustment of the armature part of the backrest, a space for play is present between the narrow sides of the wedge segments and the driver arm as a result of the operating conditions. During adjustment of the armature part, particularly upon reversal of direction, this results in an inactive stroke which is noticeable as dead travel by the user of the seat.
It is an object of the invention to improve the adjustment armature of the aforementioned kind such that the dead travel is eliminated.
This object is solved in that the driver is formed of a driver bushing and a driver ring fixedly connected thereto and comprising the driver segment, wherein the driver ring is supported on the armature part and supports, in turn, the wedge segments on its circumferential area free of the driver segment. As a result of the support of the wedge segments on the circumferential area of the driver ring that is free of the driver segment a frictional force acts as a driving moment between the driver ring and the wedge segment when a rotational movement is transmitted via the driver bushing onto the driver ring. The substantially smaller frictional moment between the wedge segments and the bearing bore, in the present case of the armature part of the backrest, acts on the outer side of the wedge segments. Up to a certain external load the frictional moment between the wedge segments and the driver ring is sufficient in order to rotate the eccentric segment and to thus adjust the armature part of the backrest. As a result of this, the armature part of the backrest can be adjusted without recognizable inactive stroke even when reversing direction. During this adjusting movement, the wedge segments, as a result of constraining forces resulting from the manufacturing process, perform a compensation movement which adapts to the geometric conditions in order to eliminate play within the bearing locations and within the tooth engagement. When now the predetermined outer load is surpassed and the frictional moment between the wedge segments and the driver ring is no longer sufficient, the rotational speed of the leading wedge segment is reduced until both wedge segments at a certain force level overcome the force storage means acting on their wide sides and impact with their wide sides on one another and thus abut one another, wherein also the driver segment of the driver ring may contact at one side a narrow side of a wedge segment, so that the armature part of the backrest is adjusted farther. Upon actuation of the driver, independent of the rotational direction, the articulated armature of the backrest is adjusted instantly. It is understood in this connection that the driver bushing must not necessarily comprise a continuous driver segment but instead can also have two spaced-apart driver cams.
Even though it is conceivable that the driver bushing and the driver ring are formed as a unitary component, it can be advantageous for assembly-technological reasons to configure the driver ring and the driver bushing of two separate armature parts which are connected to one another for torque transmission in a positive-locking way. For this purpose, the driver ring in the area of its driver segment can have a recess arranged inwardly in the radial direction which recess is engaged by at least one driver nose of the driver bushing in a torque-transmitting way.
When arranging the wedge segments on a driver ring so that they partially surround the driver ringxe2x80x94as is the case in principle for any support locationxe2x80x94the problem described in the following results. When a bushing is supported on a cylinder, as in the described prior art solution in the case of the support of the driver on the projecting collar of the armature part, both parts have usually only a single contact point acting as a support point where they contact one another as a result of the unavoidable play. This contact point will adjust always within the resultant force caused by the loading of the bearing location. When the direction of this resultant force changes, as, for example, upon pulsating loading of the seat, this contact point always will adjust to the respective effective force direction. Accordingly, the driver within the projecting collar of the armature part will roll which is noticed by the user of the seat as play within the backrest. A negative impression of the quality and a disturbance of the driver by play movements when driving are the result.
In order to counteract the aforementioned conditions, the aforementioned support lines must be placed in a defined way, which extend relative to the tooth engagement location in a certain angular position and also relative to one another in the area of the wedge segments between their inner surfaces and the circumference of the driver ring, the circumferential area of the driver ring which is not covered by the driver segment has a curvature which deviates from the curved inner surface of the wedge segments. In this way, the difference of the curvatures of the circumferential area of the driver ring which is free of the driver segment, on the one hand, and of the inner surface of each wedge segment, on the other hand, can be selected such that the resulting support points between wedge segment and driver ring have such a support point angle relative to the tooth engagement location that the effective line of the resulting support force remains within the support point angles.
In order to be able to prescribe different self-locking conditions of the wedge segments for predetermined friction pairs (inner surface of the wedge segment relative to the circumferential area of the driver ring), the center point of the driver ring and thus also its circumferential area relative to the center, i.e., the rotational axis of the driver bushing, can be moved by a minimal amount in the positive or negative direction of eccentricity. In this way, it is possible, for the same wedge angle of the wedge segment to vary the support point angle so that the possibility of optimizing the frictional connection of the system is provided. The control paths of the wedge segments now no longer depend on the support point angle of the wedge segment itself so that the inactive stroke upon actuation of the system can be influenced. When introducing a rotational movement into the driver, the wedge gap between the inner surface of the wedge segment and the circumferential area of the driver ring can be changed, wherein either the leading or trailing wedge segment is directly driven by the eccentric movement of the outer contour of the driver ring. Accordingly, the inactive stroke can be shortened so that the idle time of the adjustment is significantly reduced.
For a defined determination of the support point angle for the same curvature of the free circumferential area on the driver ring, the inner surface of each wedge segment can be divided into two areas of different curvatures which, starting at the narrow side of the wedge segment, on the one hand, and starting on the wide side of the wedge segment, on the other hand, result in a harmonically narrowing wedge gap, respectively, and the curvatures of each wedge segment meet at an apex such that it coincides with the desired support point and thus forms the contact between the wedge segment and the circumferential area of the driver ring. For a defined determination of the support point angle and for the same curvature of the inner surfaces of the wedge segments with a radius of curvature deviating relative to its external surface, whose center point can deviate from the center point of the driver, it is also possible to divide the free circumferential area of the driver ring correlated with each wedge segment into two areas with different curvatures which, in turn, meet one another at an apex which coincides with the support point and forms thus the contact between the wedge segment and the circumferential area of the driver ring. In this case, the support lines are positioned on the circumferential area of the driver. For a different position of the wedge segments the position of the support lines thus does not change and the support point angle remains the same.